VSC8124 查看數據表（PDF） - Vitesse Semiconductor

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VSC8124

2.488 Gb/s Quad Data Re-timer

Vitesse Semiconductor 

VITESSE

SEMICONDUCTOR CORPORATION

Target Specification

VSC8124

2.488 Gb/s Quad

Data Re-timer

Functional Description

Reference Clock

A clean reference clock should be provided to meet jitter specifications. An arbitrary discontinuity in refer-

ence clock phase can be tolerated without data error at slightly reduced jitter tolerance. (See Table 1) Phase

changes must not occur more often than every 20 µs. Serial data transition density must average ≥ 0.5 for that

period. Two reference clock input ports are provided. The REFSEL pin selects the active port. When REFSEL

is not driven, it floats low, selecting REFCK0. Changing REFSEL implies a phase change.

Clock Recovery

The incoming serial data on each channel is presented to a clock recovery and data re-timing circuit. For

each channel, a phase detector and low pass filter force a local clock to track the average phase of the incoming

serial data. The low pass filter is first order to prevent jitter peaking in cascaded devices.

Figure 1: Serial Input Data Eye Diagram

JT

Eye Opening

Period

Table 1: Serial Input Data Specification

Parameter

JT

JT

JT

Period

Description

Jitter tolerance

Jitter tolerance

Jitter tolerance

Min

Typ

Max

Units

Conditions

220

-

-

150

170

-

190

210

-

-

401.88

-

ps

Normal Operation

ps

Fast Lock Mode

Within 20µs after

ps

REFCLK phase

change

ps

NOTE: 1) Jitter tolerance is measured at worst case power supply and temperature, using 155.52 MHz clean reference clock

(REFCK to meet 2.0 ps RMS jitter at less than 10 Mhz in bandwidth), and 600mV swing differential PRBS data

with150ps maximum rise time.

2) Jitter tolerance and re-timed data jitter are degraded in FASTLOCK mode.

3) Reference clock frequency tolerance: ∆f <= 100 ppm

4) Jitter tolerance specifications do not apply in re-timer bypass mode.

G52271-0, Rev. 1.14

2/23/00

© VITESSE SEMICONDUCTOR CORPORATION

741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896

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